Genetic diversity analysis in indigenous rice (Oryza sativa L.) germplasm for bacterial leaf blight (Xanthomonas oryzae pv. oryzae) (BB) using resistance genes-linked markers

Among rice (Oryza sativa L.) bacterial leaf blight (BB), which is caused by Xanthomonas oryzae pv. oryzae, plays a pivotal role in decreasing rice yield. It is reported to be the most serious constraint to improving rice yield. The present investigation assessed the potentiality of BB resistance and molecular characterization of 100 rice accessions for four major BB resistance genes, viz., Xa4, xa5, xa13, and Xa21. Disease screening was carried out under glasshouse conditions using a BB culture isolated from BB-infected rice fields through the leaf clipping method. Analyses of 13 BB resistance genes linked with polymorphic microsatellites markers indicated the presence of single-, two-, three-, and four-gene combinations of xa5, xa13, Xa4, and Xa21. We found four accessions to be resistant, 34 accessions to be moderately resistant, 49 accessions to be moderately susceptible, and 13 accessions to be susceptible. Among the resistant lines, IR12L110, Namcheonbyeo, Dhalaheera, and SahbhagiDhan recorded a minimum lesion length of 3.70, 4.20, 4.67, and 8.30 cm, respectively. Phylogenetic tree, constructed using molecular data, grouped the rice germplasm into four major clusters. Resistant genes xa5 and Xa4 contributed 14 positive compatible resistant genes, each belonging to 28 germplasm for the BB resistance. The potential genetic resources identified as resistant to the BB can be used as donors for the improvement of rice bacterial blight resistance in rice breeding programs.